Scale insects

What you see

Immobile brown, grey or white bumps stuck along stems and leaf veins - most people take them for part of the plant. Scratch one with a nail: if it lifts off and is soft or juicy underneath, it is alive.

Damage

Sticky honeydew and black sooty mould coating leaves below the infestation. Yellowing, poor growth, dieback of twigs. Ants running up the trunk.

Lifecycle on this coast

One to three generations a year. Only the newly hatched crawler stage moves - once it settles and forms its shell, it is glued there for life and is protected from most sprays.

When to act

A handful of scales on a mature citrus is normal. Act when sooty mould appears or when twigs start dying back.

Months: March, April, May, June, July, August, September

Plants it bothers

Citrus, Orange, Lemon, Tangerine, Bay laurel, Olive, Apple, Peach

Natural enemies

Ladybird (Cryptolaemus), Parasitic wasp (Aphytis), Lacewing

Remedies

Horticultural oil (white oil), Insecticidal soap spray, Grease bands, Encourage predators

The thing people get wrong

Timing is everything and almost nobody gets it right: the armoured shell repels sprays, so the only vulnerable moment is the crawler stage, when the young are mobile and naked. Wrap a strip of double-sided tape on a branch - when you see tiny specks stuck to it, that is your window, and an oil spray then does more than five sprays at any other time.